Romney's rivals challenge his electability

Rivals of frontrunning Republican candidate Mitt Romney are trying to undercut the widespread perception that he's got the best chance of beating Democratic President Barack Obama in November.

In the final few days before South Carolina's potentially decisive weekend primary, Romney's rivals are focusing on their own strengths in hopes of keeping him from a third win.

Voters in the two earlier contests - the Iowa caucuses and New Hampshire primaries - said they prized a candidate's ability to beat Obama over a candidate's conservative credentials, a preference that helped Romney to his pair of victories.

Newt Gingrich unveiled a television commercial on Tuesday that starts with an announcer saying only the former speaker of the US House can defeat Obama.

The ad makes no mention of Romney, who is the former governor of Massachusetts, and instead shows Gingrich drawing cheers from the audience at Monday's debate in Myrtle Beach when he said, "More people have been put on food stamps by Barack Obama than any president in American history."

Gingrich in a speech late on Tuesday made only passing reference to Romney. Instead, he outlined his own proposals for lower taxes, less regulation and expanded domestic energy production.

"I believe I am the only candidate in this race who understands the scale of change necessary to get this country working again," Gingrich said. He predicted that if he wins the state's primary, the nomination would follow.

Former Pennsylvania senator Rick Santorum and Texas Governor Rick Perry are also hoping to change the perception of voters in the first-in-the-South primary state.

Santorum, campaigning in South Carolina, said Romney is a candidate in the mold of Bob Dole and John McCain - Republican nominees who led the party to defeat in 1996 and 2008.

"He's never run as a conservative in a general election," he said.

By contrast, Santorum said he had won a pair of elections to the House from a Democratic district in Pennsylvania, then carried the state in successive Senate campaigns, including in 2000, when George W. Bush lost the state.

The increased concentration on electability comes in the wake of polls with Iowa caucus-goers and New Hampshire primary voters, who said the ability to defeat Obama mattered more than a candidate's stands on conservative credentials, moral character or experience.

Gingrich, Santorum and Perry had all been emphasising their stands on social issues in their campaigns.

In Iowa, 31 per cent of caucus-goers interviewed for The Associated Press and the television networks said a candidate's ability to defeat Obama mattered most. Romney won the backing of nearly half of them, far outdistancing the rest of the field.

An additional 25 per cent of caucus-goers interviewed said they cared most about a candidate who was a true conservative. Romney drew the support of a mere 1 per cent of them. Among the 24 per cent who cited strong moral character, his share was 11 per cent.

The findings were roughly similar in New Hampshire, where Romney's margin of victory was larger than the slender eight-vote spread he won over Santorum in Iowa.

Thirty-five per cent of New Hampshire voters cited an ability to defeat Obama as the most important factor in deciding which candidate to support, and Romney drew the backing of 63 per cent of them.

The fifth Republican in the race is Texan Ron Paul, a libertarian who favours a sharply smaller US government and military.

A new CNN poll released on Wednesday showed Romney leading with the support of 33 per cent of likely voters, Gingrich with 23 per cent, Santorum with 19 per cent, Paul with 13 per cent and Perry with six per cent.

The four-night survey included only one night of calls after the Monday debate. Nonetheless, it showed Romney's lead dropping from 19 points two weeks ago to 10 points.

The five remaining rivals converge on Thursday in Charleston for the final debate before Saturday's primary. No Republican since 1980 has won the party's presidential nomination without first capturing the South Carolina primary.